Resetting package.loaded after a test in Lua - unit-testing

Question

I am developing unit tests in Lua and a major part of these tests is changing package.loaded. This goes from
a = require "parser"
a.b = nil
to
package.loaded["checker"] = function() return true end
And the situation where I modify an entry of package.loaded that was loaded before the test started.
I would like to reset package.loaded after every test. But I have a hard time. I tried wrapping require, which solves some problems, but does not solve the problem of the second and the third example. How can I properly make a savepoint of package.loaded right before the tests and reload that savepoint just before I start a new test? Or just roll back package.loaded to the one just after the interpeter started?

Answer 1

This is actually the answer of #EgorSkriptunoff, but he placed it as a comment.
For me, it was good enough to just make a shallow-copy of bot the package.loaded and the _G. Shallow-copy can be found here: http://lua-users.org/wiki/CopyTable:
function shallowcopy(orig)
local orig_type = type(orig)
local copy
if orig_type == 'table' then
copy = {}
for orig_key, orig_value in pairs(orig) do
copy[orig_key] = orig_value
end
else -- number, string, boolean, etc
copy = orig
end
return copy
end
The actual testing then looks like this:
local packageLoadedCopy = shallowcopy(package.loaded)
local gCopy = shallowcopy(_G)
for _, test in ipairs(tests) do
-- Do the actual test
-- Clean up the environment
local markDeletion = {}
local markModify = {}
for name in pairs(package.loaded) do
if not packageLoadedCopy[name] then
table.insert(markDeletion, name)
elseif packageLoadedCopy[name] ~= package.loaded[name] then
table.insert(markModify, name)
end
end
for _, name in pairs(markDeletion) do
package.loaded[name] = nil
end
for _, name in pairs(markModify) do
package.loaded[name] = packageLoadedCopy[name]
end
markDeletion, markModify = {}, {}
for name in pairs(_G) do
if not gCopy[name] then
table.insert(markDeletion, name)
elseif _G[name] ~= gCopy[name] then
table.insert(markModify, name)
end
end
for _, name in pairs(markDeletion) do
_G[name] = nil
end
for _, name in pairs(markModify) do
_G[name] = gCopy[name]
end
end
Do note that simply
package.loaded = packageLoadedCopy
_G = gCopy
Does not work, and I am not sure why.